In recent years there has been a growing interest in portable radios, such as two-way radios and cellular telephones. Often a portable radio user will have a need for radio communication while in a vehicle. The portable radio, when located inside the vehicle may not perform satisfactorily over long distances because either the portable antenna is insufficient or the vehicle body shields the portable antenna. Thus, the user must either purchase a separate mobile unit or use the portable radio with an external antenna through a mobile adapter.
Coupling losses associated with inserting the portable radio into the mobile adapter are a major concern in the design of any mobile adapter. Conventional methods of connecting a portable radio antenna to an external antenna often require a changeover switch which functions to disconnect or connect the internal and external antennas such that the two antennas are not connected at the same time. Switching between the two antennas, however, has a tendency to degrade the efficiency of the system. It would be an advantage to have an antenna coupler which minimizes the loses associated with inserting the portable radio into the mobile adapter.
Another disadvantage associated with many mobile adapters is that some form of power amplification, commonly known as a power "booster", is required to compensate for the coupling losses incurred when the portable radio is inserted into the mobile adapter. An antenna coupler configured to eliminate the need for additional power amplification would be a further advantage in terms of manufacturing costs and parts count.
Also, many of today's mobile adapters still require both a radio frequency (RF) contact and a ground contact on the exterior of the mobile adapter's housing in order to make the RF interconnection to the portable radio. This requires that the portable radio have at least two exposed contacts which must align within the mobile adapter housing. It would be beneficial if the number of exposed contacts could be reduced in order to ease alignment issues and reduce the exposure of radio contacts to the external environment when the portable radio is not in the adapter. A mobile adapter that included an antenna coupler which required as few interface contacts as possible would translate to fewer exposed contacts on the radio.
Accordingly, there exists a need to provide an improved antenna coupler for use in a mobile adapter which minimizes RF coupling losses using as few interface contacts as possible while eliminating the need for any additional power amplification.